JPH0675887A - Polling interval determining system - Google Patents

Abstract

PURPOSE:To provide the polling interval determining system which can execute an efficient communication, in the system for executing an inter-CPU communication through a dual port RAM by polling plural sub-CPUs with one main CPU. CONSTITUTION:A table 6 for storing the number of times of generation of a data transmitting request from respective sub-CPUs 2a, 2b, and a polling interval changing means for setting a polling interval so as to shorten a polling interval to the sub-CPU in which the number of times of generation of the data transmitting request is large by referring to the table 6 are provided on a main CPU 1 side. In accordance with the generation frequency of the transmitting request of each sub-CPU 2a, 2b, the main CPU 1 can determine a polling interval for referring to the sub-CPU, therefore, data can be transmitted and received efficiently, and the throughput of the whole system is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polling interval determination method in a system in which one main CPU unit and a plurality of sub CPU units execute inter-CPU communication by utilizing dual port RAM and polling.

[0002]

2. Description of the Related Art Conventionally, there is known a system for communicating between two CPUs via a dual port RAM.
In such a system, in hardware without an interrupt signal, a transmission / reception request flag area is provided on the dual port RAM, and both CPUs perform communication while confirming the flag area. When one main CPU unit communicates with multiple sub CPU units, the sub CPU
The side sets a transmission request flag on the dual port RAM when transmitting data to the main CPU side. Main CP
The U side checks this transmission request flag at regular intervals and receives data from the sub CPU side for which the transmission request flag is set.

FIG. 3 is an explanatory diagram of a dual port RAM communication system when there is no interrupt signal. First, sub CPU2
If there is no transmission request from b, dual port RAM3
The command "F" indicating the completion of transmission (no transmission request) is written in the transmission request flag area 8b on b. Next, when there is data to be transmitted from the sub CPU 2a to the main CPU 1, the sub CPU 2a writes a command "Q" indicating a transmission request in the transmission request flag area 8a.
The main CPU 1 always reads the transmission request flag areas on the dual port RAMs 8a and 8b via the I / O bus 5 at fixed time intervals, and if the command "F" is written, the main CPU 1 continues to read the data after a fixed time. Read the transmission request flag area of the dual port RAM. If the command "Q" has been written, the transmission request flag area of the next dual port RAM is read after a certain period of time has elapsed since the process of reading the data on the dual port RAM was executed.

[0004]

As described above, in the hardware having no interrupt signal, the main CPU and the sub CP are
In a system in which dual port RAM communication is performed between two U CPUs, the main CPU must constantly monitor the presence or absence of a transmission request from the sub CPU. FIG. 4 shows an example of the configuration of a supervisory control system using this dual port RAM communication system. The main CPU 1 is connected to a first dual port RAM 3a for communicating with the host computer 9 and a second dual port RAM 3b for communicating with the supervisory control system. First dual port R
The AM 3a is an RS- for communication with the host computer 9.
Sub CPU built into the 232C interface 10
2a. The RS-232C interface 10 receives schedule data, status request data, control data, etc. from the host computer 9. The second dual port RAM 3b is connected to the sub CPU 2b incorporated in the master station 11 of the monitoring control system. The master station 11 of the monitoring control system receives state change notification data and emergency notification data from a plurality of slave stations 12, 13, 14, 15, .... Comparing the data amounts handled by the first dual-port RAM 3a and the second dual-port RAM 3b, the schedule data is transmitted only once a day, whereas the state change notification is transmitted at regular intervals (several minutes). Come on. Therefore, the amount of communication data is completely different between the two dual port RAMs 3a and 3b, a small amount of data is communicated with the sub CPU 2a of the RS-232C interface 10, and a large amount of data is communicated with the sub CPU 2b of the monitoring control system. Will communicate. In such a case, if polling is performed at regular intervals, the sub CPU 2b, which has a larger amount of transmission data, does not complete transmission of all data, and data is accumulated in the transmission buffer. A phenomenon occurs and the throughput of the entire system does not improve.

The present invention has been made in view of the above points, and an object thereof is one main C
In a system that communicates between a PU and a plurality of sub CPUs via a dual port RAM, it is efficient by dynamically changing the polling interval to each sub CPU at regular intervals according to the communication frequency of each sub CPU. It is to provide a polling interval determination method that enables secure communication.

[0006]

According to the polling interval determination method of the present invention, in order to solve the above-mentioned problems, one main CPU 1 has a plurality of sub CPUs 2 as shown in FIG.
Dual port R by polling a and 2b
In a system that performs inter-CPU communication via the AMs 3a and 3b, a table 6 that stores the number of times of data transmission requests from the sub CPUs 2a and 2b, and the number of times of data transmission requests that occur by referring to the table 6 The main CP is a polling interval changing means for setting the polling interval so as to shorten the polling interval to the sub CPU.
It is characterized in that it is provided on the U1 side.

[0007]

In the system of FIG. 1, when the sub CPU 2a has a small number of accesses and the sub CPU 2b has a large number of accesses, the main CPU 1 moves to the sub CPUs 2a and 2b.
Is polled at the same intervals, the total data processing completion time is as shown in FIG. In the figure, Ta is the sub CP
The data reception time of U2a, Tb is the data reception time of the sub CPU 2b, and To indicates that there is no transmission request. In this example, data is received twice from the sub CPU 2a and data is received 5 times from the sub CPU 2b.
In such a case, if the polling interval of the sub CPU 2b that is frequently accessed is shortened, the total data processing completion time required to receive the same data becomes shorter as shown in FIG. 2 (B). As a result, the main CPU
The amount of data that 1 can receive increases, and the throughput also improves.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the polling interval determination method of the present invention includes a main CPU 1 and a plurality of sub CPUs 2a and 2b.
, A plurality of dual port RAMs 3a and 3b, and a sub C
A PU access count table 6 and a polling interval table 7 are provided. The main CPU 1 has a dual port RAM 3 of each sub CPU 2a, 2b at regular time intervals.
The transmission request flags 8a and 8b on a and 3b are checked. Whenever there is a transmission request from the sub CPUs 2a and 2b and the data is received, the main CPU 1
Corresponding sub-CP in U access count table 6
Increment the U access count. The access count table 6 stores the numbers of the subunits 4a, 4b, ... Comprising the sub CPUs 2a, 2b, ... And the access counts for the subunits in association with each other. The main CPU 1 refers to the access count table 6 at a constant time interval, and when the ratio of the access counts of a certain sub CPU 2a, 2b reaches a certain level or higher, the sub CPU
The polling interval table 7 is changed so as to shorten the polling interval for 2a and 2b. The polling interval table 7 stores the numbers of the subunits 4a, 4b, ... Comprising the sub CPUs 2a, 2b, ... And the polling intervals for the subunits in association with each other. The main CPU 1 refers to the polling interval table 7 every fixed number of polls, and performs subsequent polling according to the referred value. That is, the sub CPU that is frequently accessed
Polling is performed at short intervals, and sub CPUs with low access counts are polled at long intervals.
As a result, efficient data transmission / reception can be performed.

[0009]

According to the polling interval determination method of the present invention,
According to the frequency of transmission requests from each sub CPU, the main C
Since the PU can determine the polling interval for referring to the sub CPU, efficient data transmission / reception can be performed, and the throughput of the entire system can be improved.

[Brief description of drawings]

FIG. 1 is a functional explanatory diagram of a polling interval determination method of the present invention.

FIG. 2 is an operation explanatory diagram of the present invention.

FIG. 3 is an explanatory diagram of a conventional dual port RAM communication system.

FIG. 4 is a block diagram showing a configuration example of a conventional supervisory control system.

[Explanation of symbols]

 1 Main CPU 2a, 2b Sub CPU 3a, 3b Dual port RAM 4a, 4b Sub unit 5 I / O bus 6 Access count table 7 Polling interval table

Claims (1)

[Claims] 1. A main CPU has a plurality of sub-CPs.
In a system that performs inter-CPU communication via dual port RAM by polling U, each sub C
A table that stores the number of times of data transmission requests from the PU, and a polling interval changing unit that refers to this table to set the polling interval so as to shorten the polling interval to the sub CPUs that frequently generate data transmission requests Is provided on the main CPU side, a polling interval determination method.